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e73050503

Denys Vlasenko

2021-10-05

SUCCESS Duration: 163s

Subject

tls: P256 code shrink

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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Commit Diff GitHub →

networking/tls_sp_c32.c +42 -52

networking/tls_sp_c32.c+42 -52

@@ -80,13 +80,13 @@ static void sp_256_norm_10(sp_digit* a)
	}
	}

-	/* Write r as big endian to byte aray.
+	/* Write r as big endian to byte array.
	* Fixed length number of bytes written: 32
	*
	* r A single precision integer.
	* a Byte array.
	*/
-	static void sp_256_to_bin(sp_digit* r, uint8_t* a)
+	static void sp_256_to_bin_10(sp_digit* r, uint8_t* a)
	{
	int i, j, s = 0, b;

@@ -112,33 +112,28 @@ static void sp_256_to_bin(sp_digit* r, uint8_t* a)
	}
	}

-	/* Read big endian unsigned byte aray into r.
+	/* Read big endian unsigned byte array into r.
	*
	* r A single precision integer.
	* a Byte array.
	* n Number of bytes in array to read.
	*/
-	static void sp_256_from_bin(sp_digit* r, int max, const uint8_t* a, int n)
+	static void sp_256_from_bin_10(sp_digit* r, const uint8_t* a)
	{
	int i, j = 0, s = 0;

	r[0] = 0;
-	for (i = n-1; i >= 0; i--) {
+	for (i = 32 - 1; i >= 0; i--) {
	r[j] \|= ((sp_digit)a[i]) << s;
	if (s >= 18) {
	r[j] &= 0x3ffffff;
	s = 26 - s;
-	if (j + 1 >= max)
-	break;
	r[++j] = a[i] >> s;
	s = 8 - s;
	}
	else
	s += 8;
	}
-
-	for (j++; j < max; j++)
-	r[j] = 0;
	}

	/* Convert a point of big-endian 32-byte x,y pair to type sp_point. */
@@ -146,11 +141,9 @@ static void sp_256_point_from_bin2x32(sp_point* p, const uint8_t *bin2x32)
	{
	memset(p, 0, sizeof(*p));
	/p->infinity = 0;/
-	sp_256_from_bin(p->x, 2 * 10, bin2x32, 32);
-	sp_256_from_bin(p->y, 2 * 10, bin2x32 + 32, 32);
-	//static const uint8_t one[1] = { 1 };
-	//sp_256_from_bin(p->z, 2 * 10, one, 1);
-	p->z[0] = 1;
+	sp_256_from_bin_10(p->x, bin2x32);
+	sp_256_from_bin_10(p->y, bin2x32 + 32);
+	p->z[0] = 1; /* p->z = 1 */
	}

	/* Compare a with b.
@@ -195,30 +188,6 @@ static void sp_256_sub_10(sp_digit* r, const sp_digit* a, const sp_digit* b)
	r[i] = a[i] - b[i];
	}

-	/* Shift number left one bit. Bottom bit is lost. */
-	static void sp_256_rshift1_10(sp_digit* r, sp_digit* a)
-	{
-	int i;
-	for (i = 0; i < 9; i++)
-	r[i] = ((a[i] >> 1) \| (a[i + 1] << 25)) & 0x3ffffff;
-	r[9] = a[9] >> 1;
-	}
-
-	/* Mul a by scalar b and add into r. (r += a * b) */
-	static void sp_256_mul_add_10(sp_digit* r, const sp_digit* a, sp_digit b)
-	{
-	int64_t tb = b;
-	int64_t t = 0;
-	int i;
-
-	for (i = 0; i < 10; i++) {
-	t += (tb * a[i]) + r[i];
-	r[i] = t & 0x3ffffff;
-	t >>= 26;
-	}
-	r[10] += t;
-	}
-
	/* Multiply a and b into r. (r = a * b) */
	static void sp_256_mul_10(sp_digit* r, const sp_digit* a, const sp_digit* b)
	{
@@ -271,6 +240,15 @@ static void sp_256_sqr_10(sp_digit* r, const sp_digit* a)
	r[0] = (sp_digit)(c >> 26);
	}

+	/* Shift number left one bit. Bottom bit is lost. */
+	static void sp_256_rshift1_10(sp_digit* r, sp_digit* a)
+	{
+	int i;
+	for (i = 0; i < 9; i++)
+	r[i] = ((a[i] >> 1) \| (a[i + 1] << 25)) & 0x3ffffff;
+	r[9] = a[9] >> 1;
+	}
+
	/* Divide the number by 2 mod the modulus (prime). (r = a / 2 % m) */
	static void sp_256_div2_10(sp_digit* r, const sp_digit* a, const sp_digit* m)
	{
@@ -345,6 +323,20 @@ static void sp_256_mont_shift_10(sp_digit* r, const sp_digit* a)
	memset(&r[10], 0, sizeof(r) 10);
	}

+	/* Mul a by scalar b and add into r. (r += a * b) */
+	static void sp_256_mul_add_10(sp_digit* r, const sp_digit* a, sp_digit b)
+	{
+	int64_t t = 0;
+	int i;
+
+	for (i = 0; i < 10; i++) {
+	t += ((int64_t)b * a[i]) + r[i];
+	r[i] = t & 0x3ffffff;
+	t >>= 26;
+	}
+	r[10] += t;
+	}
+
	/* Reduce the number back to 256 bits using Montgomery reduction.
	*
	* a A single precision number to reduce in place.
@@ -362,7 +354,7 @@ static void sp_256_mont_reduce_10(sp_digit* a, const sp_digit* m, sp_digit mp)
	sp_256_mul_add_10(a+i, m, mu);
	a[i+1] += a[i] >> 26;
	}
-	mu = (a[i] * mp) & 0x3fffffl;
+	mu = (a[i] * mp) & 0x03fffff;
	sp_256_mul_add_10(a+i, m, mu);
	a[i+1] += a[i] >> 26;
	a[i] &= 0x3ffffff;
@@ -370,11 +362,11 @@ static void sp_256_mont_reduce_10(sp_digit* a, const sp_digit* m, sp_digit mp)
	else {
	for (i = 0; i < 9; i++) {
	mu = a[i] & 0x3ffffff;
-	sp_256_mul_add_10(a+i, p256_mod, mu);
+	sp_256_mul_add_10(a+i, m, mu);
	a[i+1] += a[i] >> 26;
	}
-	mu = a[i] & 0x3fffffl;
-	sp_256_mul_add_10(a+i, p256_mod, mu);
+	mu = a[i] & 0x03fffff;
+	sp_256_mul_add_10(a+i, m, mu);
	a[i+1] += a[i] >> 26;
	a[i] &= 0x3ffffff;
	}
@@ -617,7 +609,6 @@ static void sp_256_map_10(sp_point* r, sp_point* p)
	*/
	static void sp_256_proj_point_dbl_10(sp_point* r, sp_point* p)
	{
-	sp_point tp;
	sp_digit t1[2*10];
	sp_digit t2[2*10];

@@ -625,10 +616,9 @@ static void sp_256_proj_point_dbl_10(sp_point* r, sp_point* p)
	if (r != p)
	r = p; /* struct copy */

-	if (r->infinity) {
-	/* If infinity, don't double (work on dummy value) */
-	r = &tp;
-	}
+	if (r->infinity) /* If infinity, don't double */
+	return;
+
	/* T1 = Z * Z */
	sp_256_mont_sqr_10(t1, r->z, p256_mod, p256_mp_mod);
	/* Z = Y * Z */
@@ -848,7 +838,7 @@ static void sp_ecc_secret_gen_256(const sp_digit priv[10], const uint8_t *pub2x3

	sp_256_ecc_mulmod_10(point, point, priv);

-	sp_256_to_bin(point->x, out32);
+	sp_256_to_bin_10(point->x, out32);
	dump_hex("out32: %s\n", out32, 32);
	}

@@ -876,7 +866,7 @@ static void sp_256_ecc_gen_k_10(sp_digit k[10])
	#if FIXED_SECRET
	memset(buf, 0x77, sizeof(buf));
	#endif
-	sp_256_from_bin(k, 10, buf, sizeof(buf));
+	sp_256_from_bin_10(k, buf);
	#if !SIMPLIFY
	if (sp_256_cmp_10(k, p256_order2) < 0)
	break;
@@ -901,8 +891,8 @@ static void sp_ecc_make_key_256(sp_digit privkey[10], uint8_t *pubkey)

	sp_256_ecc_gen_k_10(privkey);
	sp_256_ecc_mulmod_base_10(point, privkey);
-	sp_256_to_bin(point->x, pubkey);
-	sp_256_to_bin(point->y, pubkey + 32);
+	sp_256_to_bin_10(point->x, pubkey);
+	sp_256_to_bin_10(point->y, pubkey + 32);

	memset(point, 0, sizeof(point)); //paranoia
	}